Nodular iron production



United States Patent This invention is concerned with a process for the production of nodular iron castings which are distinguished by the presence of small graphite nodules, a tight structure and the absence of hard spots in castings.

This improved nodular iron is prepared from a stock of molten metal having the following analysis:

Percent Oarbon 3.80-3.90 Silicon 2.00-2.30 Manganese 0.60-0.90 Copper Less than 0.15 Chromium -1 Less than 0.40

This alloy is maintained molten and at a temperature of approximately 2650" F. After appropriate inoculants have been added the percentage of silicon will have increased to between 2.80% and 3.10% and the metal will contain sufficient magnesium to render the structure nodular as cast.

This alloy is conventionally inoculated and handled in ladles containing about 2000 pounds of molten metal. The ladle is preheated and employed to contain the original inoculants. These original inoculants comprise 15 pounds of a magnesium containing ferro-silicon containing between 5 and 7% magnesium, about 47% silicon and the remainder, iron. Along with this inoculant, there is added to the ladle 10 pounds of a 75% ferro-silicon. The magnesium ferro-silicon and the 75% ferro-silicon is protected initially from the molten metal by covering these inoculants with 30 pounds of steel punchings.

The ladle so prepared is brought to the furnace containing the molten stock metal and in the course of 25 or 30 seconds, 800 to 1000 pounds of molten metal stock is added to the ladle. This fills the ladle approximately half full and initiates the action of the added inoculants upon the stock. When the ladle has become approximately half full, the addition of the final inoculant of 3,113,019 Patented Dec. 3, 1963 "ice 10 pounds of ferroasilicon is made. This 10 pounds of 75 ferro-silicon is added as a granular product to the stream of molten stock metal as it flows from the furnace to the ladle. The rate of addition of this material is adjusted so that the addition requires approximately the same time as is required to fill the ladle with molten stock. The ladle so prepared is then poured into castings at about 2550 F.

Molten nodular iron so prepared is now commercially cast into engine rocker arms and has produced rocker arms having a consistently superior structure and ease of machining.

We claim as our invention:

1. The process for the production of uniform and machineable nodular iron castings comprising preparing a stock of molten metal suitable for the production of nodular iron when inoculated with nodularizing agents, placing in a ladle a quantity of ferro-silicon and a quantity of magnesium bearing ferro-silicon, covering the magnesium bearing ferro-silicon and the ferro-silicon with a protecting layer of cold metallic ferrous material, filling the ladle partially with molten metal, initiating further addition of ferro-silicon to the ladle and continuing to add such ferro-silicon and molten metal simultaneously until the ladle is filled.

2. The process for the production of uniform and machineable nodular iron castings comprising preparing a stock of molten metal suitable for the production of nodular iron when inoculated with nodularizing agents, placing in a ladle a quantity of ferro-silicon and a quantity of magnesium bearing ferro-silicon, covering the magnesium bearing term-silicon and the term-silicon with a protecting layer of cold metallic ferrous material, filling the ladle approximately half full of molten metal, initiating further additions of ferro-silicon to the ladle and continuing to add such ferro-silicon and molten metal simultaneously until the ladle is filled.

References Cited in the file of this patent UNITED STATES PATENTS 2,675,308 Millis et al. Apr. 13, 1954 2,749,238 Millis et a1. June 5, 1956 2,750,284 Ihrig June 12, 1956 3,017,267 Bartson et al Ian. 16, 1962 

1. THE PROCESS FOR THE PRODUCTION OF UNIFORM AND MACHINEABLE NODULAR IRON CASTINGS COMPRISING PREPARING A STOCK OF MOLTEN METAL SUITABLE FOR THE PRODUCTION OF NODULAR IRON WHEN INOCULATED WITH NODULARIZING AGENTS, PLACING IN A LADLE A QUANTITY OF FERRO-SILICON AND A QUANTITY OF MAGNESIUM BEARING FERRO-SILICON, COVERING THE MAGNESIUM BEARING FERRO-SILICON AND THE FERRO-SILICON WITH A PROTECTING LAYER OF COLD METALLIC FERROUS MATERIAL, FILLING THE LADLE PARTIALLY WITH MOLTEN METAL, INITIATING FURTHER ADDITION OF FERRO-SILICON TO THE LADLE AND CONTAINUING TO ADD SUCH FERRO-SILICON AND MOLTEN METAL SIMULTANEOUSLY UNTIL THE LADLE IS FILLED. 